How to set up an engine service schedule by running hours (and stop missing intervals)
5 min read
Hour-based servicing is simple in principle and slips in practice. A method for setting intervals from the manufacturer's schedule, capturing hours reliably, and knowing what is due before it is overdue.
Why calendar reminders fail on boats
A boat that did 40 hours in June and 400 in August cannot be serviced on a calendar. Manufacturers specify most engine and generator work by running hours — 250, 500, 1,000 — with a calendar backstop (for example 'every 250 hours or 12 months, whichever first'). A schedule that ignores either half misses services.
Step 1 — take the intervals from the manual, not from memory
| Item | Interval (hours) | Interval (time) | Notes |
|---|---|---|---|
| Engine oil and filter | 250 | 12 months | Whichever comes first; more often in high-load charter use |
| Primary and secondary fuel filters | 250 | 12 months | Sooner if vacuum gauge or power loss indicates restriction |
| Raw-water impeller | 250 | 12 months | Replace, don't just inspect; keep a spare aboard |
| Drive belts | Inspect 250, replace 1,000 | 24 months | Check tension and cracking |
| Gearbox / saildrive oil | 250–500 | 12 months | Saildrive seals typically 5–7 years |
| Coolant (closed circuit) | 1,000 | 24 months | Flush and replace |
| Heat-exchanger and anodes | 500 | 12 months | Pencil anodes more often in warm salt water |
| Valve clearances | 500–1,000 | — | Per manufacturer |
| Air filter | 500 | 12 months | Sooner in dusty yards |
| Exhaust elbow / mixing elbow | Inspect 1,000 | 24 months | Common hidden failure point |
List every hour-based item per unit: oil and filter, fuel filters, impeller, zincs, belts, valve clearance, coolant, aftercooler, injectors, turbo inspection. Give each its hour interval and its calendar backstop. Do the same for generators; they usually run more hours than the mains.
Step 2 — decide how hours get recorded
The interval is only as good as the hour reading. The reliable pattern is to capture hours as part of something crew already do — the pre-sail or end-of-day checklist — rather than as a separate job nobody owns. Once a week is fine for a cruising boat; every trip for a charter boat.
Step 3 — set 'due soon' thresholds
Decide how far ahead you want warning. 25 hours or 30 days before due is a sensible default: enough time to order filters and book a slot, short enough that the warning is real.
Step 4 — log the service against the unit, with what was used
When the service is done, record the date, the hours, who did it, and the parts and consumables used. That entry becomes the next interval's starting point and your parts usage history — which tells you what to keep in spares.
Doing it in iVessel
Each engine and generator has its own schedule of hour- and date-based services. Hours entered from the pre-sail checklist update every schedule at once; Boat Health counts faults per equipment area and flags failures that are increasing; logging a service records the parts used and deducts them from spares. The whole thing prints as a service history.
Do all of this in iVessel — and keep it
Everything on this page is built into iVessel, so nothing lives in a notebook that can go overboard.
- Log a service from your phone with the hours, the work done and a photo — it is saved to the boat, not to a person's device, and cannot be lost when crew change.
- Parts and consumables are deducted from the boat's spares inventory as you log the service, so stock levels and reorder lists stay true.
- Every entry records who did it and when; a manager ashore sees the same history the engineer sees on board.
- Next-due is calculated automatically from the interval and the running hours, with reminders before it is overdue.
- Works offline at sea and syncs when you are back in range. iOS, Android and web.
Your first boat is free for 30 days.
Track this in iVessel — free 30-day trial
$35 per boat per month, unlimited users, 30-day free trial on your first boat.